Is that new, AB? PA used to have a specific exemption for cities of the first class, which I think was defined as having a population over 1 million - and only Philly meets that criteria. Has this exemption changed, recently?

As ChuckS has explained, you are misunderstanding the PA law. PA has state preemption -- Philadelphia cannot (legally) enact any firearms laws more restrictive than state law. (This doesn't stop them from passing them, but they have no force if tested in court.) The "city of the first class" bit is in state law, applies only to Philadelphia (Pittsburgh has a looooong way to go before they qualify), and all it does is require that you have a LTCF (License to Carry Firerms) even for open carry, whereas everywhere else in PA open carry is legal without a LTCF.